[llvm] [BOLT] Check entry point address is not in constant island (PR #163418)

[Paschalis Mpeis via llvm-commits]

https://github.com/paschalis-mpeis approved this pull request.

Thanks Ash! Yes, I was curious about an easy win; probably not as easy as #160161. But not a blocker for this patch, since BOLT would assert/crash anyway.

>  >  If input code is indeed problematic, it'll crash regardless of being ignored or not.
> 
> This should not be the case, if we are dealing with code marked as data then the input binary itself is not problematic, it's only BOLT that struggles to parse it.

To clarify: yes, that matches your use case.
I was referring to *a truly problematic* input binary though, ie an island not meant to be code or containing a bad instruction sequence.

In such cases, whether we ignore it and proceed (as in this patch), or use the branching as a heuristic, convert the marker and process it, it would crash anyway, but that wouldn't be BOLT's responsibility.

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Looks good! Give it a day or two in case there are any further comments.

https://github.com/llvm/llvm-project/pull/163418